1. Field of the Invention
The invention relates to a beam-splitting integrated optical element and an optical transmitter module.
2. Description of Related Art
With advancements in communication technologies, communication methods are no longer limited only to be implemented by using electrical signals. Recently, optical communication technologies have been developed to realize signal transmission with optical signals. Because transmission speed and distance of light is far higher and longer than electrons, optical communication technologies have gradually become the mainstream in the market. Based on high bandwidth requirements, demands for optical transmitter modules capable of transmitting massive amount of optical signal become higher each day. To ensure stability in the signal transmission, the optical transmitter modules often need to synchronously monitor the optical power. The optical transmitter modules using the edge emitting laser can use the back emitting light to monitor the front emitting light (i.e., the light used for transmission), so as to synchronously monitor the optical power. The optical transmitter module using the surface emitting laser must utilize optical elements to split the transmitted light in order to monitor the optical power. Therefore, the design of beam-splitting integrated optical element plays a fairly important role.
FIG. 1 is a schematic cross-sectional view of a conventional optical transmitter module. Referring to FIG. 1, an optical transmitter module 10 includes an optical element 12, lenses 14A, 14B and 14C, a light source 16 and an optical detector 18. A beam B emitted by the light source 16 is collimated by the lens 14A before entering the optical element 12 and then being transmitted to total internal reflection surfaces TIR1 and TIR2. Bottom edges of the total internal reflection surfaces TIR1 and TIR2 are connected and perpendicular to each other, such that a vertex X is formed. The beam B is split by the total internal reflection surfaces TIR1 and TIR2 and the vertex X to be transmitted towards different directions, wherein the beam B reflected by the total internal reflection surface TIR1 is converged into an optical fiber F through the lens 14B to be applicable for the signal transmission. On the other hand, the beam B reflected by the total internal reflection surface TIR2 is converged into the optical detector 18 through the lens 14C to be applicable for monitoring the optical power. In other words, the optical transmitter module 10 is capable of conducting the signal transmission and monitoring the optical power synchronously.
Since the vertex X formed by connecting the total internal reflection surfaces TIR1 and TIR2 together are prone to have curvature due to manufacturing process factors, the beam B is prone to be scattered at the vertex X, resulting in an optical power loss and a beam-splitting ratio offset thereby lowering a yield rate of the optical transmitter module 10. Further, during the assembly process of the optical transmitter module 10, a passive machine alignment is usually performed by viewing an image of the light source 16 through the lens 14B corresponding to the optical fiber F. However, in the architecture of the optical transmitter module 10, the entire image of the light source 16 cannot be viewed through the lens 14B since only a portion of the image of the light source 16 can be guided to the lens 14B through the total internal reflection surface TIR1, such that an alignment difficulty and a calibration time may both be increased during the assembly process. Accordingly, how to solve the aforementioned problems has become one of important issues in the related art.